Pharmacologic strategies in the treatment of experimental spinal cord injury

Remarkable advances have been made in pharmacologic treatments of acute and chronic spinal cord injury. The recent National Acute Spinal Cord Injury Study (NASCIS) showed that very high dose methylprednisolone given within 8 hr after injury improves neurologic recovery. The mechanism is believed to be inhibition of lipid peroxidation. Many other drugs have been claimed to be beneficial in animal studies, including other lipid peroxidation inhibitors, free radical scavengers, opiate receptor blockers, NMDA receptor blockers, calcium channel blockers, inhibitors of arachidonic acid metabolism, and protease inhibitors. In chronic spinal cord injury, much progress also has been made. Myelin was found to possess factors that inhibit axonal regeneration. Blocking these factors enhances spinal cord regeneration. Monosialic gangliosides (GM1) were recently found to improve neurologic recovery in spinal-cord-injured patients. Given as late as 48-72 hr after injury, the mechanism of action is not well understood. However, the GM1 results give hope that recovery mechanisms can be manipulated pharmacologically. Nonregenerative therapy for chronic spinal cord injury is also being developed. Several drugs, including 4-aminopyridine and baclofen, respectively blockers of potassium channels and GABA-B receptors, improve conduction in demyelinated axons. These drugs may be useful for identifying patients who might benefit from remyelination therapy. Finally, NASCIS has complicated acute spinal cord injury studies. To bring a drug to clinical trial, an investigator must now determine the optimal treatment dose, timing, and duration over a range of injury severities, in comparison and combination with methylprednisolone. This requirement has so increased the scale of drug testing that multicenter laboratory trials may be necessary.